Scarabaeiformia

Scarabaeoidea

Scarabs, stag beetles, dung beetles, rain beetles, etc.

This tree diagram shows the relationships between several groups of organisms.

The root of the current tree connects the organisms featured in this tree to their containing group and the rest of the Tree of Life. The basal branching point in the tree represents the ancestor of the other groups in the tree. This ancestor diversified over time into several descendent subgroups, which are represented as internal nodes and terminal taxa to the right.

You can click on the root to travel down the Tree of Life all the way to the root of all Life, and you can click on the names of descendent subgroups to travel up the Tree of Life all the way to individual species.

Characteristics

Perhaps the most well-known features of adult scarabaeoids are
their 3-7 segmented, fan-like or lamellate antennal club and
powerful legs armed with teeth on the outer edge, an adaptation
for digging.

Click on an image to view larger version & data in a new window

Left: Antenna of Polyphylla; most scarabaeoids have more compact clubs. Right: Leg of a scarab.

The larvae are typically C-shaped when immobile.

In addition adult scarabaeoids are distinguished by: a
highly modified, burrowing prothorax, with large coxae (almost
always with concealed trochantins and closed cavities) and
usually dentate tibiae with only one spur; hind wings with
reduced venation and strong intrinsic spring mechanism for
folding; a lamellate antennal club; no hind coxal plates; the
second abdominal sternite represented by a lateral portion only;
the eighth tergite forming a true pygidium and not concealed by
the seventh; four Malpighian tubules (Lawrence & Britton 1991);
and 1Ax-2Ax articulation mediated by a well-developed 2Ax medial
groove and dorsal ridges (Browne 1993).

Scarabaeoids feed on most types of dung and a wide range of
plant and animal matter, from detritus through lower plants to
virtually all higher plant tissues and carrion to predation on
other insects. Their habits range from free-living through fairly
sophisticated forms of brood care to sub-social behaviour (Borror
et al. 1989, Scholtz 1990).

Discussion of Phylogenetic Relationships

Scarabaeoid family and subfamily definitions were
established by the beginning of this century as were some notions
on the evolutionary progression of the taxa. However, these
concepts were often intuitively derived (confirmation of many of
these traditional ideas has subsequently occurred). The first
tangible contributions towards a phylogeny of the Scarabaeoidea
were provided by the numerous morphological studies of
the superfamily. Apart from providing vital morphological data
a rough evolutionary picture of the superfamily also emerged.

The first attempt to apply modern cladistic techniques to
the analysis of relationships within the group as a whole was
that of Howden (1982). This study, based on 39 characters from
17 taxa, focused on the phylogenetic position of Taurocerastinae
(Geotrupidae) in relation to many other scarabaeoid taxa. The
study did fulfill one of its major functions in stimulating
further investigations of the relationships among the various
higher taxa.

The next major study, that of Scholtz (1990), provided a
comprehensive review of the available scarabeoid literature.
Although the main purpose of this work was to make available a
complete data set for future cladistic analysis, some discussion
of evolutionary trends was also included.

Browne (1993) and Browne & Scholtz (1995) examined the
evolution and morphology of the hind wing articulation, base and
venation. Although this study examined all higher scarabaeoid
taxa (13 families, most subfamilies, 250 genera) and all taxa
identified by Scholtz (1990) as being of uncertain phylogenetic
status for the first time, it was very limited in that the
resulting phylogram was based on only three character complexes
(73 characters). However, there is strong evidence that wing
related characters are the most reliable of all structures in
elucidating relationships among higher taxa (Kukalov?-Peck
1983).

To date the most comprehensive study is that of Browne &
Scholtz (in preparation). They considered all major character
suites, 134 characters, which supported most of the relationships
presented by Browne (1993) and Browne & Scholtz (1995). The main
conclusions of this study are given in the phylogram above.

Although relationships among many taxa are controversial,
recent analyses, especially those of Howden (1982), Browne
(1993), Scholtz et al. (1994), Browne & Scholtz (1995, in
preparation) have resolved the following:

Glaresidae is the sistergroup of the remaining scarabaeoids
and likely reflects the ancestral scarabaeoid due to its large
number of unusual plesiomorphies.

Lucanidae and Diphyllostomatidae together form the
sistergroup of the Passalidae.

Geotrupidae (Geotrupinae, Taurocerastinae and Lethrinae),
Hybosoridae, Ceratocanthidae and Ochodaeidae together form the
sistergroup of Passalidae, Lucanidae, Diphyllostomatidae,
Trogidae, Bolboceratidae, Pleocomidae and Glaphyridae. Together
these taxa form the sistergroup of the Scarabaeidae.

However, the following are still heatedly debated:

Monophyly of the Geotrupidae. Howden (1982) includes
Bolboceratinae, Geotrupinae, Taurocerastinae and Lethrinae in
this family. Scholtz & Browne (in press) present evidence that
this family is polyphyletic and elevated Bolboceratinae to
familial status.

The position of Glaphyridae. Once accorded superfamily status
(Hinton 1967) this family has more commonly been placed among the
so-called "intermediate" scarabaeoids (Geotrupidae, Hybosoridae,
Ceratocanthidae and Ochodaeidae)(Scholtz 1990). Recent evidence
suggests that it is a member of the so-called "primitive"
scarabaeoids (Passalidae, Lucanidae, Diphyllostomatidae,
Trogidae, Bolboceratidae, Pleocomidae and Glaphyridae).

Other Names for Scarabaeoidea

Scarabaeiformia

Scarabs, stag beetles, dung beetles, rain beetles, etc.

Lamellicornia

References

Areekull, S. 1957. The comparative internal larval anatomy of several genera of Scarabaeidae (Coleoptera). Annals of the Entomological Society of America 50: 562-577.

Arnett, R.H., 1968. The beetles of the United States. Ann Arbor, The American Entomological Institute.

Browne, D.J. 1993. Phylogenetic significance of the hind wing basal articulation of the Scarabaeoidea (Coleoptera). Ph.D. thesis, University of Pretoria.

Browne, D.J. and C.H. Scholtz. 1995. Phylogeny of the families of Scarabaeoidea (Coleoptera) based on characters of the hindwing articulation, hindwing base and wing venation. Systematic Entomology 20(3):

Holloway, B.A. 1972. The systematic position of the genus Diphyllostoma Fall (Coleoptera: Scarabaeoidea). New Zealand Journal of Science 15: 31-38.

Howden, H.F. 1982. Larval and adult characters of Frickius Germain, its relationship to the Geotrupini, and a phylogeny of some major taxa in the Scarabaeoidea (Insecta: Coleoptera). Canadian Journal of Zoology 60: 2713-2724.

Howden, H.F. and J.F. Lawrence. 1974. The New World Aesalinae, with notes on the North American lucanid subfamilies (Coleoptera, Lucanidae). Canadian Journal of Zoology, 52(12): 1505-1510.

Ratcliffe, B.C. 1984. A review of the Penichrolucaninae with analyses of phylogeny and biogeography, and a description of a second New World species from the Amazon Basin (Coleoptera: Lucanidae). Quaestiones Entomologicae 20: 60-87.

Each ToL branch page provides a synopsis of the characteristics of
a group of organisms representing a branch of the Tree of Life. The
major distinction between a branch and a leaf of
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descendent branches, that is, subgroups representing distinct genetic
lineages.